beak question-underbite? anyone ever had one with success??

I have a chick still in the egg, my hatch ended, so I thought. I opened the remaining 4 eggs with no movement. I got to the 4th egg and it's alive! I examined it real quick and noticed it has a lower beak longer than the top. I didn't know if I should cull or not, or just leave it and see what happens. We hate to cull and do so as a last resort but don't want the chick to starve, suffer etc. I didn't know how far you can safely cut a beak back, just to make it even, it's about an 1/8 inch bigger. I recovered the hole with a clean piece from another egg, above the pip line so that won't be an issue. Ideas, suggestions appreciated

Krista

 

ugh, forget it. As I went to get a better look at it I noticed it's head was open, I could see it's brain. We(dh) culled . I should have known something was up when it didn't really blink it's eyes much
Krista